As his mind drifts back to The Meeting, Tommy Kelly nods and grins. He remembers the intensity in the room, the dead-weight seriousness of the discussion.

“Basically,” says Kelly, looking like a man recalling a childhood reprimand he deserved, “it was about cleaning up my act.”

The Meeting was an offseason session between Kelly and new Raiders defensive line coach Mike Waufle, a 32-year coaching veteran who had returned from New York after holding the same job in Oakland from 1998 through 2003, one year before Kelly arrived.

After six seasons with the Giants, where he coached such premier talents as Michael Strahan and Osi Umenyiora and Justin Tuck, Waufle was back at Raiders headquarters, an ex-Marine fixing his severe gaze on someone deemed crucial to success.

Waufle knew of Kelly’s reputation as an overweight, overpaid, underachieving tackle; that stuff gets around the NFL. But he also knew how good Kelly could be.

So what followed was equal parts pep talk and scolding, a no-nonsense motivational warning shot. Kelly’s career was at a crossroads, and this was a blatant attempt to flip his internal switch, to summon the vast potential buried within his 6-foot-5, 330-pound body.

Eight months later, having shed 25 pounds and gained a new attitude, Kelly’s potential has become production. It’s on display every time the ball is snapped. Even as he toils in the trenches, his impact stands out.

Once emblematic of what ailed Oakland’s defense and the team as a whole, Kelly now is the centerpiece of a unit that can dominate a game.

Though the professional resurrection of Philadelphia Eagles star Michael Vick is an amazing thing to witness — six years after signing the richest contract in NFL history ($130 million for 10 years in Atlanta), he’s becoming the quarterback many thought he could be — Kelly is accomplishing a similarly stunning though much less dramatic recovery.

Thirty months after signing the biggest contract ever for a defensive lineman ($50.5 million over seven years, $18,125,000 guaranteed) and 23 months after being arrested for suspicion of DUI, he reported to camp vowing to be one of the best in the league — and he has been.

“He’s playing very well,” Waufle says quietly. “I’m happy with him. We’re all happy for him.”

Opponents rave about Kelly’s energy. Teammates marvel at his consistency. Kelly is pleased with the notice but acutely aware of a reputation he knows he earned on merit.

“I had to sit back and (accept) I was doing more damage to myself than anybody else was,” he says. “I had to look myself in the mirror. I was deflecting a lot of blame last year. I had to come off that.”

Kelly, 30, traces his troubles back to reconstructive surgery on his right knee in 2007. He gained weight and, for a while, thought it would make him more effective in the interior line. Sometime last season, it became apparent this was not working.

Moreover, time was slipping away. Though he signed with Oakland as an undrafted free agent from Mississippi State in 2004, Kelly noticed that several defensive tackles drafted in ’04 — New England’s Vince Wilfork and Arizona’s Darnell Dockett to name two — were building impressive careers, and believed he, too, should be making an impact.

He would have to, if the Raiders were to appreciably improve the heart of their defense. As good as fellow tackle Richard Seymour is, one terrific lineman can be neutralized. Two, lined up next to each other, can terrorize.

“Big Rich hit me up before the season started,” Kelly says. “He was texting me, talking about ‘Let’s go out there and be the best two D-tackles in the league.’ I know I definitely didn’t want to be anybody’s weak link.”

And that’s what he had been, certainly in relation to his salary. Not only did Raiders boss Al Davis choose an odd time to offer the contract — while Kelly was rehabbing — but the obscene dollar amount made Kelly the subject of ridicule. NFL defensive linemen celebrated the new salary ceiling, but Raiders fans waited for the payoff.

It’s here at last. Despite frequent double-teams, Kelly leads AFC tackles in sacks with seven and ranks among position leaders in tackles with 52.

The former basketball player at Provine High in Jackson, Miss., has become the “monster” former Raiders teammate Warren Sapp said he would be. Patriots coach Bill Belichick, perhaps the most respected defensive mind in the NFL, said in 2006 that Kelly was “one of the best defensive linemen in the league.” He is the player Davis thought he could be.

Sapp and Belichick and Davis had seen enough of Kelly’s best to know how good he could be. They weren’t wrong, just premature.

Now that Kelly is dedicated to raising his own standard, anybody can see it, on most every play.

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